The present disclosure relates to a method for the resistive cell equalization of battery cells of a battery, to a battery having at least two battery cells and an apparatus for battery control, and to a motor vehicle.
A large number of battery cells is usually connected in series in batteries in order to achieve a sufficiently high output voltage for the respective application. The series connection of battery cells means it is necessary for an output current of the battery to flow in all battery cells.
On account of the leakage currents of different magnitudes or a different total capacity of the individual battery cells, the states of charge of said battery cells differ from one another.
In order to achieve optimum and reliable utilization of the battery capacity, it is therefore necessary to ensure that the current state of charge of the battery cells in relation to one another is as identical as possible. In order to achieve this, what is known as balancing (cell equalization or charge equalization) is periodically carried out. In this case, the states of charge of the battery cells are influenced by charging or discharging such that a uniform state of charge is achieved.
A conventional method for balancing is resistive balancing, in which a portion of the charge of the cells which are excessively charged is converted into thermal energy in an electrical resistor, that is to say the state of charge of the battery cells is changed to a uniform level by deliberate reduction in individual battery cells. In this case, each battery cell has its own balancing resistor between the poles, it being possible for said balancing resistor to be activated by means of an electrical switch. These balancing resistors are usually located in a controller and are activated as required. In this case, a large number of resistors are generally activated at the same time.
The high thermal power which is produced locally on an activated balancing resistor may result in considerable heating of the resistors and their surrounding area, in particular of the printed circuit board as well. The associated absolute increase in temperature and the aging of the resistors which is caused by a change in temperature can lead to destruction of balancing resistors, adjacent components or solder connections and the like.
US 2011/0109269 A1 discloses a circuit and a method for resistive balancing in battery cells.